Field of the Invention
The present disclosure relates to a fixing device used in an electrophotographic image forming apparatus.
Description of the Related Art
In recent years, a fixing device that uses a cylindrical belt is increasing with the aim to suppress the heat capacity of the fixing device. Furthermore, there is a device that adopts an electromagnetic induction heating method in order to increase the rate of temperature rise of the belt. Japanese Patent Laid-Open No. 2011-154232 describes a fixing device that uses a belt and that adopts an electromagnetic induction heating method.
A fixing device that uses a belt needs to dispose a stay inside the belt in order to form a fixing nip portion. Since the stay needs to be rigid, the stay is typically made of metal.
However, magnetic flux concentrates inside a spiral coil. As is the case of Japanese Patent Laid-Open No. 2011-154232, when a stay is disposed inside a coil, eddy current occurs in the stay due to magnetic flux concentrating inside the coil, disadvantageously resulting in generation of heat in the stay.
Such an issue is not limited to fixing devices that use a belt and the same issue can be encountered even in a device that uses, rather than a belt, a roller with high rigidity, when a stay is disposed inside a roller.